Pumping apparatus



Nov.'24, 1942. FERGUSON 2,302,847

I PUMPING APPARATUS Filed May 12, 1937 I 5 Sheets-Sheet l r I I 2017JEN/6n 5 07. aflzarand 7 .N 1942 A. D. FERGUSON 2502 847 IIPUMPINGAPPARATUS Filed May 12', 195'? sSMQtS-snQQt 2 Nov. 24, 1942. A. D.FERGUSON' I PUMPING APPARATUS Filed May 12, 1937 3 Sheets-Sheetdhranderflizywaiz.

Patented Nov. 24, 1942 zsmm some arransrus Alexander D. Ferguson,Michigan City, Ind., assignor to Sullivan Machinery Company, acorporation of Massachusetts Application May 1:, 1037, Serial 110.142,.Claims. (oi, sac-2s) My invention relates to pumping apparatus,

' and more particularly to pumping apparatus having improved means foreffecting a variable delivery of pumped fluid while maintaining anapproximately uniform rate of actuation;

' It is naturally desirable, if economically practicable, to provide apumping apparatus in which a wide variation in the quantity of fluidpumped may be effected while at the same time maintaining emcientoperation and avoiding excessive heating of the COmPXGSSlbIB fluid beingpumped. Numerous attempts in this direction have been made, and I havedevised an improved apparatus working on this general principle andadapted to effect partial unloading of pumping apparatus, such as an aircompressor, by interrupting admission through the inlet for all or adeflnite part of the suction strokes of the pump piston, and I haveprovided improved controlling means which enables a variation in theportion of the suction strokes during which no fluid enters the pumpcylinder, and have made the control, in a preferred form, automatic, inaccordance with the variations in pressure of the pump discharge.

Apparatus for controlling unloading which does not alter materially thestructure of the inlet and discharge valve mechanism per se and whichmay be merely superimposed upon them, is obviously ofa very advantageousnature, and I have provided a device which, while allowing the use ofautomatic inlet valve devices, permits the interruption of the intake 01fluid to be pumped, at substantially any desired point in the suctionstroke, thereby reducing the quantity of pumped fluid delivered uponeach of the compression strokes of the pump or compressor. .Desirably,such an apparatus assumes the form of an auxiliary shut-oil valve whichmay be caused to seat virtually instantaneously, but which, whenunseated, neither interferes with the efficient working of thecompressor nor is subjected to forces making it diflicult to maintain itin open position. Desirably, means is provided for electricallycontrolling such a valve, and the controlling means may advantageouslycomprise means actuated in synchronismwith the compressor or pump insuch a way as to insure the rupting admission of fluid to the pump at asubstantially uniform time in the working cycle, while allowing it tobecome operative to interrupt the intake of fluid at any point duringthe suction stroke, depending upon the value of the pump dischargepressure. The contr may be made directly responsive to the dischargepressure, if desired, by a servo-motor controlling the position of asuitable contact device, or may be made responsive to the variations inpressure of the pump discharge-over and above a certain minimum value,as, for example, by providing a suitable pop type valve which will open,let us say, when the compressor discharge pressure attains a value ofone hundred pounds and simply permit the building up at its dischargeside of pressures in excess of one hundred pounds.

An object of my invention is to provide an im= proved pumping apparatus..Another object of my invention is to provide an improved pumping"apparatus having improved means for varying the duration of, and, ifdesired, wholly interrupting, the intake of fluid to be pumped duringeach cycle of operation of said pumping apparatus. I

A further object of my invention is to provide an improved pumpingapparatus having automatic inlet and discharge valves and improved meansso-to-speak superimposed upon the inlet valve mechanism and operative tocut ofl automatically the access of fluid to be pumped, to said inletvalve, at a desired time in the suction stroke of the pumping'apparatus.-A still further object of my invention is to provide an improvedauxrendering inoperative of the device for interiliary unloadingapparatus of the electrically operated type embodying a valve which ismovable to interrupt the access of fluid to be pumped, to the inletvalve mechanism of the pump. Yet a further object of my invention is toprovidean improved auxiliary valve device controlling the admissionoffluid tobe pumped, toapump cylinder, having improved controlling meansregulating the'portions of a suction stroke during which the same isoperative. Still another object of my invention is to provide animproved flow-controlling valve particularly adapted for use incontrolling the unloading of a pump or compressor, having improvedelectrical actuating means and of an improved construction, whereby thesame is free from harmful interference with fluid flow and likewisesubjected degree to-the influence of flowing fluid. Other objects andadvantages oi my invention will hereinaiter more fully appear.

In the accompanying drawings, in which one iorm of my invention is shownfor purposes of illustration,

Fla. 1 is a view, partially in side elevation and partially in section,showing a pumping apparatus constructed in accordance with my invention.

toaminimum view through a combined inlet and discharge valve mechanismarranged at one end of a compressor cylinder and provided with improvedcontrolling means constructed in accordance with the illustrativeembodiment of the invention.

Fig. 3 is a view, with parts broken away, primarily on the plane of thesection line 3-3 of Fig. 2.

Fig. 4 is a section on the plane of the line 4-4 01 Fig. 3.

Fig. 5 is a section on the plane of the line 5--5 of Fi 2.

Fig. 6 is a top view, but with certain parts shown in section, of aportion of the electrical controlling apparatus.

Fig.7 is a side view of the same apparatus, with parts broken away, thisview being taken on the plane of the section line 1-1 of Fig. 6.

Fig. 8 is a fragmentary section on the plane of the line 88 of Fig. 7.

Fig. 9 is a fragmentary section on the plane of the line 8-9 of Fig. 7.

Fig. 10 is a section on the plane of the line l0 ll of Fig. 6, with theview turned through 90 so that the parts correspond to Fig. 8.

Fig. 11 is a section on the plane of the line li-H of Fig. 7.

Fig. 12 is a section on the l2l2 of ig. 6.

Fig. 13 is a wiring diagram.

Fig. 14 is a diagrammatic view showing a deslrable mode of controllingpressure supply.

In the drawings, a suitable base 1 supports a compressor, generallydesignated 2, having a cylplane 01' the line inder, generally designated3, containing in its bore 4 a piston Land discharging through a line 3'to a suitable point of use or storage, herein exemplifled by thereceiver 1. The compressor cylinder has heads 8 and 9 providing intakechambers l0, and has a discharge chamber II which is connected with thedischarge line 6. Suitable automatic inlet and discharge valvemechanisms l2 and I3 are provided at each end of the compressorcylinder-herein, the compressor is of the double-acting type- -eachbeing supported by a stud l4 and held to said stud by suitable nuts 15and i8.

The discharge valve mechanism l3 comprises a usual ported seat elementI1, a guard element It, a guide element i9, and annular valve 20, and asuitably flexed valve spring 2|; the parts being held in cooperativerelation ,by cap screws 22. The inlet valve mechanism i2 diflers from ausual inlet valve mechanism frequently used in such compressors, only inthat the seat element is made of non-magnetic material, such as brass,aluminum, or the like. Herein, it will be noted that this valvemechanism comprises a ported seat element providing a seat 25surrounding ports 21 and adapted to have a valve 28 cooperate therewith.The valve is normally maintained in closed position by a spring 29,which is in turn held in position by a guard plate 30. The movements ofthe valve are guided by a suitable guide element 3| which is clampedbetween the seat element 25 and the guard element 30 by cap screws 32.

Obviously, upon the suction strokes of the piston 5, air or other fluidto be pumped will pass from the intake chamber l0 through the ports 21,past the unseated valve 28, and into the compressor cylinder; and uponthe discharge strokes the compressed fluid will unseat the valve 20 andpass to the discharge chamber ii and through the discharge line 6 to thereceiver 1.

electromagnet 38 associated with said valve; said valve element 31,however, when released adapted to seat upon coaxial seat surfaces 39,upon the member 25, between which the ports 21 extend.

The structure of the device .35 may obviously vary, and herein I haveshown the winding 40 0t an electromagnet enclosed in a suitablemetallicdesirably steelcasing 4| and having secured to its face a brass,phosphor-bronze, aluminum or other non-magnetic front cover 42. Thisfront cover is grooved, as at 43, to provide a wide annular recess 44adapted to receive the valve 31, which is of magnetic material. Ifdesired, there may be formed integrally with the cover 42, or separatelytherefrom, as shown in the drawing, an annular, grooved valve springreceiving and guiding portion 45, having a groove 46 lacing the valveand receiving a suitable transversely or annularly flexed annular springelement 41 which is desirably of non-magnetic material. If the portionbe made separately, as indicated in the drawing, from the cover 42, andset into the latter, so to speak, and made of magnetic material, it isdesirable that the spring, which is of non-magnetic material, shall begreater in thickness than the depth of the spring-receiving groove, asotherwise the residual magnetism may tend to cause the valve 31 toremain in the position shown in Figs. 2 and 4. It is to be noted thatthe groove 44 is made 01 such depth, and the spring guiding portions ofsuch small projection, that the valve 31 may occupy a position with-itsouter surface in a plane with the outer rim of the cover 42. The cover42 may be held in position by screws 48 or in some other suitablemanner; and the member 41 is desirably traversed by-a series of openings48 arranged about its axis, in communication with another series ofopenings 50 in an intermediate member 5|, which is clamped by the .nut[5 between the member 4| and the seat element 25. The member 5i may beformed to provide by its external periphery a guiding action for theinner edge of the valve 31; or, as illustrated, guiding projections 52may be provided suitably spaced about the inner periphery of the covermember 42 to guide the valve during both its seating and its unseatingmovements. It will be noted that devices 35 are provided for each end ofthe double-acting cylinder shown in Fig. 1, and controlling mechanismfor each of these devices is also provided so that they may operate inproper relation to the compression cycles of their respective cylinderends'.

For the purpose of energizing the magnets 40 periodically at appropriatetimes and maintaining them energized for the desired portions of thesuction strokes, the apparatus shown'in Figs. 6 to 13 is provided.Suitably mounted for rotation in a definite timed relation to the crankshaft of the compressor, herein for rotation at the same angular ratewith and directly by the compressor crank shaft, is a rotating cylinder55, which will be noted to be mounted by a flange 56 and a fixedsocketed connection 51 coaxial with the fly wheel and crank shaft of thecompressor. The member 55 is desirably formed of insulating material,and is provided with a pair of plates 59 and 59 of conducting materialmounted upon its periphery. These will be noted to be arranged, so tospeak, in staggered relation; that is to say, they are more or lessarranged, except for annular portions 60, 60' thereof which will shortlybe noted, on opposite arcuate portions of the surface of the cylinder.Plates 59 and 59' include, in addition to the annular portions 60, 60respectively thereof, tapering portions Bi and Bi respectively, thesetapering portions each having a leading edge, numbered 62 and 62respectively, for the different plates, and a helically disposedtrailing edge, numbered 63 and 63' respectively, for the diiferentplates. Accordingly, at the ends of the plates remote from their annularportions the plates die away to points, and at the ends of the taperingportion nearer the annular portions, these tapering portions areapproximately 180 in circumferential extent with respect-to the cylindermember 55. The periphery of themember 55 is so formed, as by recessing,that the cylindrically bent plates may have their outer surfaces flushwith the cylindrical surface of the cylindrical member. The two platesare electrically connected in any suitable manner, as by the bus bar 64which may be arranged within the body of the cylinder 55. Each of theplates 59 and 59' has an adjustable brush cooperatingtherewith, andsince the plates are electrically connected, a single stationary brushmay coact directly with either of the plates and function in conjunctionwith the adjustable brushes which are individual to the plates. Thestationary brush 65 is mounted to cooperate with the annular portion 60of the plate 59, and the adjustable brushes 86 and 66' cooperaterespectively with the plates 59 and 59'. The several brushes are carriedupon a stationary carriage generally designated 61, which comprises apair of parallel supporting rods 68 which extend through relativelystationary support brackets 69. A sliding brush support is mounted toslide upon the rods 68 and carries the sliding brushes 66 and 66. Thestationary brush 65 is mounted by means of the spring-actuated brushholder II to contact with the rotating annular portion 60 of the plate59. The brushes 66 and 86 are resiliently pressed against the peripheryof the rotating cylinder 55 and the plates 59 and 59' thereon, bysuitable spring brush holders 1! and 12' respectively. Herein, it willbe noted that the several brush holders 'are pivotable about pins I3,13' and 13" and have springs 14, I4 and 14" acting upon them and uponstationary pins 15, I5 and 15" to force the brushes yieldingly againstthe periphery of the rotating contacts. The brushes 56 and 66' aremounted upon the sliding carriage It, as above noted, and this carriageis movable longitudinally by a rod 11, which carries at one end thereofa piston 10 reciprocable in a cylinder bore 19 formed in a cylindermember 80 which is supported in fixed relation to the frame of thecompressor and in parallelism with the guiding rods 68. Suitable springmeans 8| is provided normally to maintain the piston 18 in such aposition that the brushes 66 and 68' may be in contact with the annularportions 60 and 86' respectively of the plates 59 and 59', when there isno pressure supplied to the cylinder bore 19 in excess of the desiredminimum working pressure of the compressor.

suitable reduced operating pressure bearing a, definite relation to thecompressor discharge pressure, may be supplied from the receiver 1through means herein represented by the fluid delivery connection 82shown as leading from the receiver to a port 83 in the end of thecylinder 00. As the compressor discharge pressure increases, the pistonII will move the carriage II to theright in Figs. 6 and 7 and instead ofthe magnets 88 being energized throughout the complete cycle of pistonmovement. the magnets will be energized for progressively smallerportions of the suction strokes of the compressor piston, as thedischarge pressure rises. In order to have the desired range of movementof the movable contacts, it will be found better in practice, probably,to use a popf valve in the line 82', to provide a continuous bleed forthis line, and to transmit to the cylinder 80 only the excess pressure-above the desired minimum compressor discharge pressure. Such anarrangement is shown in fragmentary detail in Fig. 14, wherein the "pop"valve will be noted to be designated 85 and the bleed port 86.

Any suitable circuits connecting the magnet windings 40, the brushes 65,66 and and 88' and the source of current, herein represented by thegenerator G, maybe employed, asior example, those shown in Fig. 13,where it will be noted that the generator is connected by conductor Mto, say, the crank end winding 40 and by a branch conductor 88 to thehead end winding 48, and by another conductor 89 to the stationary brush65. The brush 86 is connected by a conductor 80 with the opposite end ofthe'crank end winding 40, while the brush it is connected by a conductorM to the opposite end ofthe head end winding. 7 v

The mode of operation or the apparatus described will be readilyunderstood. The views or the partsinFigs. l, ZandiandFigaSandi do notcorrespond with 'each'other, being selected primarily to illustrate thestructure, but the diagram oi Fig. 13, and the position of the piston inFig. l, and of valve 8 in Figs. 2 and 4, do correspond. In the positionof the parts shown in Fig. 13, the compressor piston l is just beginningthe suction stroke in the crank end of the cylinder. The crank endmagnet winding 40 is being supplied with current through a circuitincluding generator G, conductor 88. stationary contact 85, plate 5!,adjustable brush 88, conductor 80 and the winding 40. Accordingly, thevalve plate 11 is held in the unseated position shown in Fig. 2, and airmay freely enter the crank end of the compressor cylinder past the valve28. when the crank shaft has rotated far enough to cause the trailingedge I! or the plate 58 to pass from beneath the adiustablebrush 86, themagnet ll will be deenergized, and the spring I! will start the valve 31in a closing direction, and the latter will instantly seat upon thesurfaces 3 8 and interrupt further inlet of fluid into the compressorcylinder. Accordingly, a partial vacuum will be produced during theremainder of the suction stroke or the piston, and the early portions ofthe compression stroke for the crank end of this cylinder will simplybring the pressure 20 and force the reduced quantity of iluid taken ininto the discharge line 0. During the passage Compressor dischargepressure, or preferably of the piston I from the headend of the cylinder'of the cylinder, but with a to the crans: end, there will be first anengagement between the contact plate 59 and the ad- Justable brush 66',resulting in the establishment of the circuit energizing the head end.magnet winding iii and holding the head end valve 31 in retractedposition, then a release, after a portion of the stroke is completed, ofthis valve. and an interruption thereby of inlet of fluid to the headend of the cylinder. The cycle for this end of the cylinder will be thesame as for the other end phase difierence of 180.

Obviously, ii the use of air diminishes to a sufilcient extent so thatthe compressor discharge pressure builds up to a high enough valuetomove the piston 18 far enough to the right in Figs. 6 and 7 to move theadjustable contact members 88 and 66' beyond the points at the extremeright hand ends of the plates 59 and 58', there will be no opening ofthe valves 31 at any time during the suction strokes of the piston 5,and accordingly the compressor will operate completely unloaded. It maybe noted that it the springs 41 should require assistance in effectingvirtually instantaneous closure of the valve elements 31',

it would be possible to provide for the access to' certain valveportions of the fluid flowing through the ports 21; but with theextremely short valve movement necessary to effect closing and the useof springs of substantial strength, this will not ordinarily benecessary.

It will be evident that I have shown aiconstruction in which the samecycle, except for the diil'erence in phase, will be effected at bothends of a double-acting compressor cylinder, but it will be evident thatthis apparatus may be employed with respect to but one end of thecompressor cylinder or with single-acting cylinders, if desired. Thearrangement is simple; there is no waste of power during the partiallyunloaded operation of the compressor. There is no development ofexcessive heat. An exceedingly wide range of partial unloading, and alsocomplete unloading, are possible. The magnet windings 40 are located ina place where they would be continuously maintained cool by theinflowing air, but by proper design these may be made to require nospecial cooling and they will not materially heat the air entering thecompressor cylinder. All the parts are simple in construction, easilyrepaired or replaced and definite in operation.

While I have in this application specifically described one form whichmy invention may assume in practice, it will be understood that thisform of the same is shown for purposes of illustration and that theinvention may be modified and embodied in various other forms withoutdeparting from its spirit or the .scope of the appended claims. I

What I claim as new and desire to secure by Letters Patent is:

1. In combination, in a pumping apparatus, a cylinder, a piston therein,inlet and discharge valves for said cylinder for controlling the flow offluid to and from said cylinder, and electrically-controlled valve meanshaving controlling means governed by the pump discharge pressure forautomatically interrupting inlet of fluid through said inlet valve tosaid cylinder at difierent times, depending upon the pump dischargepressure, prior to the end of the suction strokes of the pumpingapparatus.

2. In combination, in a pumping apparatus, a cylinder, a piston therein,inlet and discharge valves for said cylinder for controlling the flow offluid to and from said cylinder, and electrically-controlled valve meanshaving controlling means responsive to variations in the pump dischargepressure for automatically interrupting inlet of fluid through saidinlet valve to said cylinder for difierent portions, depending upon thepump discharge pressure, of the suction strokes of the pumpingapparatus.

3. In combination, in a pumping apparatus, a cylinder, 9, pistontherein, inlet and discharge valves for said cylinder for controllingthe flow of fluid to and from said cylinder, valve means forinterrupting the inlet of fluid through said inlet valve to saidcylinder during different portions of the suction strokes of the pumpingapparatus,'the extent of such portions depending upon the pump dischargepressure, electromagnetic controlling means for said inlet-interruptingvalve means, and pressure fluid actuated means responsive to variationsin the pump discharge pressure for automatically variably controllingsaid electromagnetic controlling means to effect interruption of inletfor increasing portions of the suction strokes as pump dischargepressure increases above a desired minimum.

4. In combination, in a pumping apparatus, a cylinder,a piston, adischarge valve, an inlet valve, an auxiliary valve coaxial with saidinlet valve and closable'to cut oil fluid access to said inlet valve,means for shielding said auxiliary valve, when open, from the rush offluid during inlet to said cylinder, means for continuously biasing saidauxiliary valve toward closed position, and a control device for openingand holding open said auxiliary valve, said control device for saidauxiliary valve coaxial with the latter.

5. In combination, in a pumping apparatus, a

cylinder, a piston, a discharge valve, an inlet valve, an auxiliaryvalve coaxial with said inlet valve and closable to cut on fluid accessto said inlet valve, and a control magnet for opening and holding opensaid auxiliary valve during'varying time intervals, said control magnetbeing arranged coaxial with said auxiliary valve and in the intake spaceof the pumping apparatus.

6. In combination, in a pumping apparatus, a cylinder, a piston, adischarge valve, an inlet valve, an auxiliary valve coaxial with saidinlet valve and closable to cut off fluid access to said inlet valve,means for shielding said auxiliary valve, when open, from the rush oi!fluid during inlet to said cylinder, mean for continuously urging saidauxiliary valve towards closed portion, and a control magnet for openingand holding open said auxiliary valve during varying time intervals,said control magnet being arranged coaxial with said auxiliary valve andin the intake space of the pumping apparatus.

7. In combination, in a valve mechanism, an inlet valve, a cage elementproviding a seat for said'valve on one sideand having an opposed seat,an auxiliary valve supported in cooperative relation to said opposedseat, springs tending to close both valves, and means for opening thesecond valve and holding it open against the action of its respectivespring.

8. In combination, in a valve mechanism, an

inlet valve, a cage element providing a seat for said valve on one sideand having an opposed seat, an auxiliary valve supported in cooperativerelation to said opposed seat, springs tending to close both valves, andmeans outside the second valve for opening the second valve andacylinder, a" piston reciprccable therein, dis- 1 spective .spring during.varying time intervals.

10. In combination, a cylinder, a piston, actu-' sting means for saidpiston including a crank shaft, automatic valve means for said cylinder;auxiliary valve means for eflecting partial or total unloading byinterrupting inlet at diiIerent points in, or throughout, the suctionstrokes of said piston, and magnetic means having a control devicerotating with the crank shaft for regulating the time of interruption oiinlet.

11. In combination, a cylinder, a piston, ac-

' tuating means'ior said piston including a crankshaft, automatic valvemeans for said cylinder, auxiliary valve means for eflecting partial ortotal unloading by interrupting inlet at diflerent points in, orthroughout, the suction strokes of said piston, and magnetic meanshaving a control device rotating with the crankshaft and "a cooperatingdischarge pressure responsive device movable longitudinally ,of said.crankshaft, tor

' controlling said auxiliary valve means.

12. In. combination, in a pumping apparatus, a cylinder, a piston, adischarge valve, an inlet.

valve, an auxiliary valve closable to cut 01! fluid access to said inletvalve, on eiectromagnet for opening and holding open said auriliaryvalve when energized, and'means responsive to pump charge valve meansfor said cylinder, a valve assembly for controlling the flow oi fluid-tosaid cylinder, said valve assembly comprising a t member having passagemeans therein for conducting fluid to said cylinder and providing seatsat the opposite ends of said passage means, an

inlet valve cooperating with one of said seats and opening in thedirection 0! flow of fluid through said passage me'ans towards saidcylinder ior c ntroll ng the flow of fluid relative to said cylinder, anauxiliary valve cooperating with the other of said seats and closing inthe direction oi flow oi fluid through said passage means towards saidcylinder for controlling the flow o! fluid towards said inlet valve, andmeans cooperating with said auxiliary valve for causing the same tooccupy its closed position during progressively increasing portions 0!the suction strokes of said piston with respect, to said inlet valve ascompressordischarge pressure rises above a predetermined value.

' 16. In a'pumping mechanism, in combination, I

a cylinder, a piston reciprocable therein, discharge valve means forsaid cylinder, means for conducting fluid to said cylinder, an

inlet valve opening in the direction 0! flow 0! fluid through saidpassage means towards said cylinder for controlling the now of fluidrelative to said cylinden an auxiliary valve closing in the direction offlow oi fluid through said pe means towards saidcylinder for-controllingthe flow oi fluid towards said inlet valve; and cooperating with saidauxiliary valve for caus the same to occupy its closed position duringpro- .-gressively increasing portions of the suction discharge pressurefor continuously energizin laid electromagnet or forenergislng saidelectromagnct at a predetermined point-in each cycle [or pistonoperation and tie-energizing said electroardiilerent points varying inonce with discharge pressure. ll. In:-eombinatlon, -in a pumpingapparatus, a cylinder, 1 piston, a discharge valve, an inletaccordstrokes of said piston with ret to said valve as comprr dischargepressure above a predetermined value, said means cooperating with saidauxiliary valve'including yielding f means iormoving the same in onedirection d means eii'ective du diflerent portionsoi such suctionstrokes as compressor discharge pr valve, an auxiliary valve closable tocut. of! fluid accesl'to said inlet valve, means for continuous- I lyurging said auxiliary valve in a closing directiomran velcctromagnet foropening and holding open said auxiliary valve when energized, and meansresponsive to pump discharge pressure torenergizing said electromagnetat a predetermined-point in'each cycle or piston operation andde-energising said electromagnet at diflerent points varying inaccordance with discharge 14. In a. pumping mechanism, in combination,

charge valve means for said cylinder, m,

means for conducting fluid to said cylinder, an

' inlet valve opening in the direction oi flow of .fluid through saidpassage means towards said cylinder for controlling the flow oi fluidrelative to said cylinder, an auxiliary valve closing in the directionof flow of fluid through vSaid passage means towards said cylinder forcontrolling the flow oi fluid through said passage means towards saidinlet valve, and means cooperating with said auxiliary valve for causingthe same to occupy its closed position during progressively increasingportions of. the suction strokes of said piston with respect to saidinlet valve as compressor discharge pressure rises above a predeterminedvalue.

. a cylinder, .a piston reciprocabletherein, disvariesior overcomingsaid yielding means and moving said auxiliary valve in the o rection.

17.- In a pumping 111 in combination, a cylinder, apiston recip ocabletherein, charge valve means for said cylinder, '1 means for conductingfluid to said cylinder, an

inlet valve 0 in the direction of flow of fluid through said 1. meanstowards said cylinder for controlling the flow of fluid relative to saidcylinder, an auxiliaryvalve closing-in the direction oi flow oifluidthrough said u means towards said cylinder for controlling e flow o!fluid towards said inletwalve, and means cooperating with said auxiliaryvalve for causing the same to occupy its closed position d progressivelyincreasing portions of the suction strokes-oi said piston with respectto said inlet valve as compressor discharge pressure rises above apredetermined value. said means cooper= ating with said auxiliary valveincluding yielding means for moving the same in one direction,

means operative on the delivery of operating medium thereto for movingsaid auxiliary valve in the opposite direction, and means governed bycompressor discharge pressure for effecting delivery oi. operatingmedium to said last mentioned means-during different portions of thesuction strokes oi said piston relative to said inlet valve apredetermined value.

15. In a pumping mechanism, in combination, (6 18. In a pumping mec, incombination,

it at a cylinder, a piston reciprocable therein, discharge valve meansfor said cylinder, a valve assembly for controlling the flow of fluid tosaid cylinder, said valve assembly having passage means therein forconducting fluid to said cylinder, an inlet valve opening in thedirection of fluid flow through said passage means for controllingtheflow of fluid relative to said cylinder, an auxiliary valve closing inthe direction 01 fluid flow through said passage means for controllingthe flow of fluid to said inlet valve, and controlling means for saidauxiliary valve including means for effecting opening of said auxiliaryvalve during portions of the cycles of reciprocatory movement of saidpiston in said cylinder, means for eflecting closure of said auxiliaryvalve during the remaining portions of the cycles of reciprocatorymovement of said piston in said cylinder, and means governed bycompressor discharge pressure for varying said portions inversely.

19. 'In a pumping mechanism, in combination, a cylinder, a pistonreciprocable therein, a valve assembly for controlling thesflow of fluidto said cylinder, said valve assembly having passage.

means therein for conducting fluid to said cylinder, an inlet valveopening in the direction of fluid flow through said passage means forcontrolling the flow o1 fluid relative to said cylinder, an auxiliaryvalve closing in the direction of fluid flow through said passage meansfor controlling the flow of fluid to said inlet valve, and means foropening said auxiliary valve during portions of the suction strokes ofsaid piston and for closing the same during subsequent-portions of thesame suction strokes when compressor discharge pressure exceeds apredetermined value, said last mentioned means including meansresponsive to compressor discharge pressure variations for altering theproportions of such suction strokes during which said auxiliary valve isopen.

20. In combination, in a pumping apparatus,

a cylinder, 8. piston reciprocable in said cylinder, 7

a discharge valve, and valve mechanism for controlling the flow oi!fluid to said cylinder, said valve mechanism including avalve platetraversed by an intake port and having an annular valve seat surroundingsaid intake port at one side of said plate and another annular .valveseat surrounding said intake port at the other side of said valve plate,an annular inlet valve cooperating with the valve seat surrounding thecylinder end of said port and opening when the pressure on said inlet,valve adjacent said intake port exceeds the pressure on said valveadjacent said cylinder for admitting-fluid to the latter, an annularvalve coaxial with said inlet valve and cooperating with the otherannular valve seat. for controlling the flow of fluid to said inletvalve,

and means for eflecting a closure of said last mentioned valve duringportions of the suction strokes of said piston varying with compressordischarge pressure.

ALEXANDER D. I IIZIRtGUS ON.

